Filters
Results 1 - 10 of 351
Results 1 - 10 of 351.
Search took: 0.026 seconds
| Sort by: date | relevance |
[en] Dapsone (DDS) forms a 1:1 supramolecular complex with β-cyclodextrin (β-CD) both in the absence and presence of linear alcohols. The apparent association constants (Kapp) were measured using a steady-state fluorescence method. Kapp decreases linearly with an increasing number of carbon atoms in the chain of the alcohol. We attribute this to a competition between dapsone and linear alcohol for the β-CD hydrophobic cavity as detailed analysis of Kapp as a function of the concentration of alcohol suggests that the interactions in the β-CD-dapsone-linear alcohol system do not result in the formation of ternary supramolecular complex. Quenching the fluorescence of dapsone with NaI shows that the β-CD cavity acts as a shield against contact between dapsone and this aqueous phase quencher, while addition of alcohols inhibits this protective effect. This again suggests that alcohols occupy the space within the β-CD cavity with the result that dapsone molecules are forced to reside in the aqueous environment. Based on the significant enhancement of the fluorescence intensity of dapsone produced through complex formation, a spectrofluorimetric method for the determination of dapsone in bulk aqueous solution in the presence of β-CD is developed. The linear relationship between the fluorescence intensity and dapsone concentration was obtained in the range of 3.39 to 1.50x103 ng ml-1, with a correlation coefficient (r) of 0.9998. The detection limit was 1.02 ng ml-1. There was no interference from the excipients normally used in tablet formulations. The application of the present method to the determination of dapsone in tablets and human plasma gave satisfactory results and was compared with the pharmacopoeia method
Journal
[en] This essay discusses how to develop departments of nuclear medicine in mountainous areas in West China. The developments need the leaders' supports, doctors' understanding and patients' trust. And it is also very important to improve doctors' skills of diagnosis and treatment, and the management of medical quality, and overcome inconveniences in transportation and communication. At the same time, more projects such as radionuclide imaging, radioimmunoassay, radionuclide treatment and personnel training should be also key contents in the development of departments of nuclear medicine in these areas
Journal
Asian Journal of Nuclear Medicine; ISSN 1607-680X; 
; v. 1(4); p. 269-270
; v. 1(4); p. 269-270
[en] The transport properties of the three scenarios of the strained graphene magnetic barriers, where the first one is composed of the strained stripe in the positive magnetic field and the pristine stripe in the negative magnetic field on the left and right sides respectively, the second one is just the result of exchanging the stripes in the first one, and the last one contains the fully strained stripes on both sides, have been investigated. It is found that the first two configurations own the same evolution behavior both in transmission and conductance versus the strain, the joint contributions from the strains in the first two configurations lead to the enhancement both in transmission and conductance in the third one. The strain tends to devastate the regular shape of the energy bands within the scope of higher momentum/energy, where the more severe damage is observed in the superlattices with the fully strained periodic unit cell. The uniformity of the periodic unit between the left and right stripes in the third scenario makes the energy gaps of the superlattices diminish and even disappear in contrast to its first two counterparts, where the discrepancy between the strained stripe on the left side and pristine stripe on the right side increases the inhomogeneity, and thus the energy gaps.
Journal
[en] Γδ,X and Γδ,Ka values of over 800 kinds of nuclides, which could transmit photons, were recalculated in this study based on their decay schemes, the quality-energy absorption coefficients of air to photons and the newest data of W value. The results were obviously different from those calculated before at about 2% deviation. The authors also calculated Γδ,H (peripheral dose equivalent ratio constant) and Γδ,H (directional dose equivalent ratio constant), respectively, by using the conversion coefficients given in ICRU-47 report
Journal
Chinese Journal of Radiological Health; ISSN 1004-714X; ; v. 7(3); p. 129-130
; v. 7(3); p. 129-130
[en] A brief pulse of red (R) radiation increased activity and protein content of photosphoenolpyruvate carboxylase (PEPC): this increase was inhibited by cycloheximide. The effect of R was far-red pulse (FR) reversible when R was followed immediately by FR. Thus phytochrome was involved in PEPC regulation in etiolated maize leaves. Both a lag phase and a saturation exists in the process of R induction of PEPC synthesis: the highest PEPC activity was obtained 24 h after R. Etiolated maize leaves of different age showed different sensitivity to R: the highest sensitivity was found in 5 d-old seedlings. 5 min of R was sufficient for inducing PEPC synthesis, and no additional increases were obtained in activity and protein content of PEPC when the R time was prolonged
Journal
Photosynthetica; ISSN 0300-3604; ; v. 28(1); p. 83-90
; v. 28(1); p. 83-90
[en] Highlights: • Chlorination kinetics of three benzophenone-type UV filters (BPs) was studied. • Chlorination of BPs followed second-order reaction. • The transformation products (TPs) of six BPs were identified. • Several transformation pathways were proposed. • Mostly enhanced toxicity of TPs after chlorination was observed. - Abstract: The present study focused on the kinetics, transformation pathways and toxicity of several benzophenone-type ultraviolet filters (BPs) during the water chlorination disinfection process. The transformation kinetics of the studied three BPs was found to be second-order reaction, which was dependent on the concentration of BPs and chlorine. The second-order rate constants increased from 86.7 to 975 M"−"1 s"−"1 for oxybenzone, 49.6–261.7 M"−"1 s"−"1 for 4-hydroxybenzophenone and 51.7–540 M"−"1 s"−"1 for 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid with the increasing pH value from 6 to 8 of the chlorination disinfection condition. Then the transformation products (TPs) of these BPs were identified by HPLC-QTof analysis. Several transformation pathways, including electrophilic substitution, methoxyl substitution, ketone groups oxidation, hydrolysis, decarboxylation and ring cleavage reaction, were speculated to participate in the chlorination transformation process. Finally, according to the toxicity experiment on luminescent bacteria, Photobacterium phosphoreum, enhanced toxicity was observed for almost all the TPs of the studied BPs except for 2,2′-dihydroxy-4,4′-dimethoxybenzophenone; it suggested the formation of TPs with more toxic than the parent compounds during the chlorination process. The present study provided a foundation to understand the transformation of BPs during chlorination disinfection process, and was of great significance to the drinking water safety.
Journal
| 1 | 2 | 3 | Next |